They also help to report on strikes and monitor the type of planes flying overhead.

The volunteers have incurred the wrath of both the Russians and also the Syrian president.

The White Helmets have also been nominated for the Nobel Peace Prize. "What did they achieve in Syria?" Assad asked upon hearing about their nomination.

Sources believe that The White Helmets were attacked because of winning the humanitarian aid award.

"The prize angered the regime and the Russians and they intentionally hit us today," Ibrahim al-Hajj, a White Helmet volunteer, said. "In spite of all that, we will keep working and be stronger."

Fierce bombing continued in a second night of strikes on the Syrian city since the disintegration of the ceasefire.

"The bombs made very big holes that the people of Aleppo have not witnessed before and the explosions were very fierce," Mujahed Abu Goud, an activist at the Aleppo Media Centre, said. "The bombs are made to destroy basements as they can dig several metres in the ground."

The powerful explosives used in the bombing are said to be capable of targeting underground bunkers used by hospitals.

A White Helmet Volunteer said that one of their centres, a fuel depot, three hospitals, apartment buildings as well as emergency trucks were destroyed. Workers reported that the wounded remained trapped in the debris.

The volunteer rescue group are said to have saved more than 60,000 Syrians, with 141 White Helmets losing their lives in their efforts to help the dying and wounded.